package com.pig.easy.bpm.utils;

import java.net.InetAddress;
import java.net.UnknownHostException;
import java.security.MessageDigest;
import java.security.NoSuchAlgorithmException;
import java.security.SecureRandom;
import java.util.Random;

/**
 * todo:
 *
 * @author : pig
 * @date : 2020/8/10 15:26
 */
public class RandomGUID extends Object {
    public String valueBeforeMD5 = "";

    public String valueAfterMD5 = "";

    private static Random myRand;

    private static SecureRandom mySecureRand;

    private static String s_id;

    /*
     * Static block to take care of one time secureRandom seed. It takes a few seconds to initialize
     * SecureRandom. You might want to consider removing this static block or replacing it with a
     * "time since first loaded" seed to reduce this time. This block will run only once per JVM
     * instance.
     */

    static {
        mySecureRand = new SecureRandom();
        long secureInitializer = mySecureRand.nextLong();
        myRand = new Random(secureInitializer);
        try {
            s_id = InetAddress.getLocalHost().toString();
        } catch (UnknownHostException e) {
            e.printStackTrace();
        }

    }

    /*
     * Default constructor. With no specification of security option, this constructor defaults to
     * lower security, high performance.
     */
    public RandomGUID() {
        getRandomGUID(false);
    }

    /*
     * Constructor with security option. Setting secure true enables each random number generated to
     * be cryptographically strong. Secure false defaults to the standard Random function seeded
     * with a single cryptographically strong random number.
     */
    public RandomGUID(boolean secure) {
        getRandomGUID(secure);
    }

    /*
     * 随机生成GUID码
     */
    private void getRandomGUID(boolean secure) {
        MessageDigest md5 = null;
        StringBuffer sbValueBeforeMD5 = new StringBuffer();

        try {
            md5 = MessageDigest.getInstance("MD5");
        } catch (NoSuchAlgorithmException e) {
            System.out.println("Error: " + e);
        }

        try {
            long time = System.currentTimeMillis();
            long rand = 0;

            if (secure) {
                rand = mySecureRand.nextLong();
            } else {
                rand = myRand.nextLong();
            }

// This StringBuffer can be a long as you need; the MD5
// hash will always return 128 bits. You can change
// the seed to include anything you want here.
// You could even stream a file through the MD5 making
// the odds of guessing it at least as great as that
// of guessing the contents of the file!
            sbValueBeforeMD5.append(s_id);
            sbValueBeforeMD5.append(":");
            sbValueBeforeMD5.append(Long.toString(time));
            sbValueBeforeMD5.append(":");
            sbValueBeforeMD5.append(Long.toString(rand));

            valueBeforeMD5 = sbValueBeforeMD5.toString();
            md5.update(valueBeforeMD5.getBytes());

            byte[] array = md5.digest();
            StringBuffer sb = new StringBuffer();
            for (int j = 0; j < array.length; ++j) {
                int b = array[j] & 0xFF;
                if (b < 0x10) sb.append('0');
                sb.append(Integer.toHexString(b));
            }

            valueAfterMD5 = sb.toString();

        } catch (Exception e) {
            System.out.println("Error:" + e);
        }
    }

    /*
     * 转换成标准的GUID码
     *例如: C2FEEEAC-CFCD-11D1-8B05-00600806D9B6
     */
    public String toString() {
        String raw = valueAfterMD5.toUpperCase();
        StringBuffer sb = new StringBuffer();
        /*
         * sb.append(raw.substring(0, 8)); sb.append("-"); sb.append(raw.substring(8, 12));
         * sb.append("-"); sb.append(raw.substring(12, 16)); sb.append("-");
         * sb.append(raw.substring(16, 20)); sb.append("-"); sb.append(raw.substring(20));
         */
        sb.append(raw);
        return sb.toString();
    }

    /*
     * Demonstraton and self test of class
     */
    public static void main(String args[]) throws Exception {
        RandomGUID myGUID = new RandomGUID();
        System.out.println(myGUID.toString());
        myGUID = new RandomGUID();
        System.out.println(myGUID.toString());
/*
Thread.sleep(10000);
for (int i = 0; i < 1000; i++)
{
RandomGUID myGUID = new RandomGUID();
// System.out.println("Seeding String=" + myGUID.valueBeforeMD5);
// System.out.println("rawGUID=" + myGUID.valueAfterMD5);
// System.out.println("RandomGUID=" + myGUID.toString());

System.out.println(myGUID.toString());
// System.out.println(myGUID.toString().replaceAll("-", ""));

}
*/
    }
}
